One example of a conventional erect image lens devices for magnifying displayed image is a device in which a plurality of distributed-index rod lenses are arranged in one dimension. In this erect image magnifying lens device, each optical axis of the rod lenses is arranged in an angle so as to implement desired magnification of the lens device, and the working distance of each rod lens is adjusted in such a manner that images passed through respective rod lenses are formed on a same plane.
Another example of a conventional erect image magnifying lens device comprises the combination of an erect image, unity magnification lens and a fresnel lens, the erect image, unity magnification lens consisting of a plurality of distributed-index rod lenses arranged in two dimensions on the same plane. FIG. 1 shows such an erect image magnifying lens device. The lens device 8 comprises an erect image, unity magnification lens 10 consisted of a plurality of distributed-index rod lenses arranged in two dimensions on the same plane, a concave fresnel lens 12 positioned within the working distance of the rod lens, a display element 14, and an image plane 16.
According to the lens device 8, the light emitted from the display element 14 is transmitted through the rod lenses 10, is refracted by the concave fresnel lens 12, and reaches to the image plane 16 on which a large magnified image is formed.
In the first conventional lens device comprising the plurality of distributed-index rod lenses arranged in one dimension, it is impossible to form a two-dimensional device because the adjustment of the optical axis angle and the working distance of the rod lens is difficult.
In the second conventional lens device comprising the combination of the erect image, unity magnification lens and the concave fresnel lens, it is difficult to obtain higher magnification since the magnification obtained is only 1.1-1.2 by refracting the light within the working distance of the erect image, unity magnification lens with the concave fresnel lens. When a plurality of erect image magnifying lens devices are arranged in two dimensions to form an image display apparatus having a large screen, if the magnification of the erect image magnifying lens device is low, it is difficult to make a display element small so that the cost of the lens device becomes high. Also, if the light is caused to be refracted by the concave fresnel lens in a large angle so as to obtain a higher magnification, there is a problem such that an image displayed around the peripheral portion of an image plane gets blurred.
While the both of conventional lens devices have the construction utilizing rod lenses, the processing for rod lenses is very difficult.
The object of the present invention, therefore, is to provide an erect image magnifying lens device which may obtain a higher magnification.
Another object of the present invention is to provide an erect image magnifying lens device having a superior image forming capability without decreasing an image quality of the peripheral portion of an image plane.
Still another object of the present invention is to provide an erect image magnifying lens device using a micro-lens array which may be easily formed by a molding process.